a report to high level construction ltd. a soil ... investigation report... · borehole logs ......

A REPORT TO HIGH LEVEL CONSTRUCTION LTD.

A SOIL INVESTIGATION FOR RESIDENTIAL DEVELOPMENT

3879 TOWN LINE

CITY OF ORILLIA

REFERENCE NO. 1606-S168

AUGUST 2016 DISTRIBUTION 3 Copies - High Level Construction Ltd. 1 Copy - Soil Engineers Ltd. (Toronto)

Reference No. 1606-S168 ii

TABLE OF CONTENTS

1.0 INTRODUCTION ................................................................................... 1

2.0 SITE AND PROJECT DESCRIPTION .................................................. 2

3.0 FIELD WORK ........................................................................................ 3

4.0 SUBSURFACE CONDITIONS .............................................................. 4

4.1 Topsoil ............................................................................................ 4 4.2 Sand ................................................................................................ 5 4.3 Silty Sand Till ................................................................................. 6 4.4 Sandy Silt Till ................................................................................. 7 4.5 Compaction Characteristics of the Revealed Soils ........................ 9

5.0 GROUNDWATER CONDITIONS ........................................................ 11

6.0 DISCUSSION AND RECOMMENDATIONS ...................................... 13

6.1 Foundations .................................................................................... 15 6.2 Engineered Fill ............................................................................... 16 6.3 Basement and Slab-On-Grade ........................................................ 19 6.4 Underground Services .................................................................... 20 6.5 Backfilling in Trenches and Excavated Areas ............................... 21 6.6 Garages, Driveways, Interlocking Stone Pavement and

Landscaping .................................................................................... 24 6.7 Pavement Design ............................................................................ 25 6.8 Stormwater Management Pond ...................................................... 26 6.9 Soil Parameters ............................................................................... 28 6.10 Excavation ..................................................................................... 28

7.0 LIMITATIONS OF REPORT ................................................................. 30

Reference No. 1606-S168 iii

TABLES

Table 1 - Estimated Water Content for Compaction ........................................ 9

Table 2 - Groundwater Levels ........................................................................... 11

Table 3 - Founding Levels ................................................................................ 15

Table 4 - Pavement Design ............................................................................... 25

Table 5 - Coefficients of Permeability and Infiltration Rates .......................... 27

Table 6 - Soil Parameters .................................................................................. 28

Table 7 - Classification of Soils for Excavation ............................................... 29

DIAGRAM Diagram 1 - Frost Protection Measures (Garage) ............................................. 24

ENCLOSURES Borehole Logs .......................................................................... Figures 1 to 4 Grain Size Distribution Graphs ............................................... Figure 5 Borehole Location Plan .......................................................... Drawing No. 1 Subsurface Profile .................................................................... Drawing No. 2

Reference No. 1606-S168 1

1.0 INTRODUCTION

In accordance with a written authorization dated March 22, 2016 from Mr. David

Meeks, President of High Level Construction Ltd., a soil investigation was carried

out at a property located on the east side of Town Line and south of Millwood Road,

in the City of Orillia, for a proposed residential development.

The purpose of the investigation was to reveal the subsurface conditions and

determine the engineering properties of the disclosed soils for the proposed

development.

The geotechnical findings and resulting recommendations are presented in this

Report.


2.0 SITE AND PROJECT DESCRIPTION

City of Orillia is located within the periphery of Lake Simcoe basin where the glacial

till has been partly eroded in places, by glacial Lake Algonquin and filled with

lacustrine silts and clay.

The subject site is almost rectangular in shape, encompasses an area of 27.4 ac

(11.1 ha), having a municipal address of 3879 Town Line, City of Orillia. It is a

wooded area with a dense growth of mature trees. The existing ground surface is

undulated, generally descends to the east, with a maximum grade difference of nearly

12 m between Boreholes 1 and 4.

It is understood that a residential development is planned for this site, with municipal

services, paved access roadways, and a stormwater management pond located at the

northeast corner of the site. Details of the development, however, were not available

at the time this report was prepared.


3.0 FIELD WORK

The field work, consisting of drilling 4 boreholes to depths of 6.3 m and 7.8 m, was

performed on July 19, 2016, at the locations shown on the Borehole Location Plan,

Drawing No. 1. Due to the heavy growth of trees, a temporary access was created

through the centre of the site for the drilling program.

The holes were advanced at intervals to the sampling depths by a track-mounted,

continuous-flight power-auger machine equipped for soil sampling. Standard

Penetration Tests, using the procedures described on the enclosed “List of

Abbreviations and Terms”, were performed at the sampling depths. The test results

are recorded as the Standard Penetration Resistance (or ‘N’ values) of the subsoil.

The relative density of the granular strata and the consistency of the cohesive strata

are inferred from the ‘N’ values. Split-spoon samples were recovered for soil

classification and laboratory testing.

Upon completion of drilling, monitoring wells, consisting of 50-mm diameter PVC

pipes were installed in the boreholes for future groundwater monitoring and

hydrogeological study purpose.

The field work was supervised and the findings were recorded by a Geotechnical

Technician.

The elevation at each of the borehole locations was surveyed using hand-held Global

Navigation Satellite System surveying equipment (Trimble Geoexplorer 6000 series)

with an accuracy of 0.1± m.


4.0 SUBSURFACE CONDITIONS

Detailed descriptions of the encountered subsurface conditions are presented on the

Borehole Logs, comprising Figures 1 to 4, inclusive. The revealed stratigraphy is

plotted on the Subsurface Profile, Drawing No. 2, and the engineering properties of

the disclosed soils are discussed herein.

This investigation has disclosed that beneath a veneer of topsoil, the site is generally

underlain by strata of silty sand till and sandy silt till, with embedded sand and silt

seams and layers at various depths and locations.

4.1 Topsoil (All Boreholes)

The revealed topsoil is 20 to 25 cm in thickness. It is dark brown in colour, showing

that it contains appreciable amounts of roots and humus. These materials are

unstable and compressible under loads; therefore, the topsoil is considered to be void

of engineering value but can be used for general landscaping purposes.

Due to its humus content, the topsoil will generate an offensive odour under

anaerobic conditions and may produce volatile gases; therefore, it must not be buried

within the building envelope, or deeper than 1.2 m below the finished grade, as it

may have an adverse impact on the environmental well-being of the development.

The topsoil can only be reused in landscaping purpose. A fertility analysis can be

carried out to further assess the suitability of topsoil for re-use as a planting soil or

sodding medium.


4.2 Sand (Boreholes 1, 3 and 4)

A layer of sand was encountered beneath the topsoil, extending to depths of 0.7 m

and 1.3 m below ground. Sample examination indicates that it is fine grained in

Boreholes 1 and 3, fine to coarse grained in Borehole 4. The sand is a non-cohesive

material and its sorted structure indicates that it is a glaciolacustrine deposit.

The natural water content of the samples was found to range from 4% to 12%, with a

median of 9%, showing that the sand is in a damp to very moist, generally moist

condition.

The obtained ‘N’ values range from 3 to 6, with a median of 3 blows per 30 cm of

penetration, indicating that the relative density of the sand is very loose, probably

loosened by the weathering process.

Based on the above findings, the following engineering properties of the sand is

deduced:

• Medium frost susceptibility and low soil adfreezing potential.

• High water erodibility under seepage pressure.

• Relatively pervious, with an estimated coefficient of permeability of 10-3 cm/sec,

an average infiltration rate of 50 mm/hr, and runoff coefficients of:

Slope

0% - 2% 0.04

2% - 6% 0.09

6% + 0.13

• A frictional soil, its shear strength is derived from its internal friction angle and

is soil density dependent.

Reference No. 1606-S168 6 • In steep cuts, the sand will slough to its angle of repose, run under seepage

pressure and boil with a piezometric head of 0.4 m.

• A fair pavement-supportive material, with an estimated California Bearing Ratio

(CBR) value of 15%.

• Moderately low corrosivity to buried metal, with an estimated electrical

resistivity of 6000 ohm·cm.

4.3 Silty Sand Till (All Boreholes)

The silty sand till was encountered below the topsoil or sand deposit in the upper to

mid section of the revealed stratigraphy. It consists of a random mixture of soils; the

particle sizes range from clay to gravel, with sand being the dominant fraction. It is

heterogeneous in structure, indicating that it is a glacial deposit. The silty sand till

contains occasional sand and silt seams and layers, cobbles and boulders.

The obtained ‘N’ values range from 3 to 100, with a median of 14 blows per 30 cm of

penetration, showing the sand till is very loose to very dense, being generally

compact. The loose till is restricted to the weathered zone up to a depth of 2.0 m.

The natural water content of the soil samples was determined and the results are

plotted on the Borehole Logs; the values range from 8% to 30%, with a median of

11%, indicating that the till is in a damp to wet, generally moist condition.

Grain size analyses were performed on 2 representative samples of the silty sand till;

the result is plotted on Figure 5.

Based on the above findings, the following engineering properties are deduced:

• Highly frost susceptible and moderately water erodible.

Reference No. 1606-S168 7 • The laminated sand and silt layers are water erodible.

• Relatively low permeability, with an estimated coefficient of permeability of

10-5 cm/sec, an average infiltration rate of 15 mm/hr, and runoff coefficients

of:

Slope

0% - 2% 0.11

2% - 6% 0.16

6% + 0.23

• Frictional soil, its shear strength is primarily derived from internal friction, and

is augmented by cementation. Therefore, its strength is density dependent.

• It will generally be stable in a relatively steep cut; however, prolonged

exposure will allow the sand and silt layers to become saturated, which may

lead to localized sloughing.

• Fair pavement-supportive material, with an estimated CBR value of 10%.

• Moderately low corrosivity to buried metal, with an estimated electrical


4.4 Sandy Silt Till (All Boreholes)

The sandy silt till was encountered in the lower zone of the revealed stratigraphy,

extending to the maximum investigated depth of the boreholes. It consists of a

random mixture of particle sizes ranging from clay to gravel, with silt being the

dominant fraction. The soil is heterogeneous in structure, showing it is a glacial

deposit.

Sample examinations disclosed that the till is slightly cemented and display slight to

some cohesion when remoulded, indicating that the clay content varies. The samples

slaked readily when placed in water and, when shaken, the samples displayed a low

Reference No. 1606-S168 8 dilatancy. Occasional sand and silt seams and layers were found in the soil samples,

and some of them were wet.

Hard resistance to augering was encountered, showing that occasional cobbles and

boulders are embedded in the till mantle. The obtained ‘N’ values range from 27 to

100, with a median of 100 blows per 30 cm of penetration, indicating the relative

density of the till deposits is compact to very dense, being generally very dense.

The natural water content of the soil samples was determined and the results are

plotted on the Borehole Logs. The values range from 5% to 14%, with a median of

8%, indicating that the tills are in a damp to moist, generally in a damp condition.

Accordingly, the engineering properties relating to the project are given below:

• Moderately high frost susceptible and moderately water erodible.

• Low permeability, with an estimated coefficient of permeability of

10-6 cm/sec, and runoff coefficients of:

Slope

0% - 2% 0.15

2% - 6% 0.20

6% + 0.28

• Frictional soil, the shear strength is primarily derived from internal friction,

and is augmented by cementation. Therefore, its strength is density dependent.

• It will be stable in relatively steep cuts; however, under prolonged exposure,

localized sheet collapse will likely occur.

• A fair pavement-supportive material, with an estimated CBR value of 8%.

• Moderate low corrosivity to buried metal, with an estimated electrical



4.5 Compaction Characteristics of the Revealed Soils

The obtainable degree of compaction is primarily dependent on the soil moisture and,

to a lesser extent, on the type of compactor used and the effort applied.

As a general guide, the typical water content values of the revealed soils for Standard

Proctor compaction are presented in Table 1.

Table 1 - Estimated Water Content for Compaction

Soil Type

Determined Natural Water Content (%)

Water Content (%) for Standard Proctor Compaction

100% (optimum) Range for 95% or +

Sand 4 to 12 (median 9) 11 5 to 14

Silty Sand Till 8 to 30 (median 11) 12 6 to 15

Sandy Silt Till 5 to 14 (median 8) 13 8 to 17

Based on the above findings, the in situ soils are generally suitable for a 95% or +

Standard Proctor compaction. A portion of the silty sand till is too wet and will

require aeration prior to structural compaction. The aeration can be effectively

carried out by spreading the wet soil thinly on the ground in the dry, warm weather.

A portion of the sandy silt till is too dry and will require the addition of water for

structural compaction.

The weathered soil must be sorted free of topsoil and rootlets inclusions prior to its

use a structural backfill. The native soils should be compacted using a heavy-weight,

knead-type roller. The thickness of each lift should be limited to 20 cm before

Reference No. 1606-S168 10 compaction or to a suitable thickness assessed by test strips performed by the

equipment which will be used at the time of construction.

When compacting chunks of till, the compactive energy will frequently bridge over

the chunks in the soil and be transmitted laterally into the soil mantle. Therefore, the

lifts of this soil must be limited to 20 cm or less (before compaction). It is difficult to

monitor the lifts of backfill placed in deep trenches; therefore, it is preferable that the

compaction of backfill at depths over 1.0 m below the road subgrade be carried out

on the wet side of the optimum. This would allow a wider latitude of lift thickness.

If the compaction of the soils is carried out with the water content within the range

for 95% Standard Proctor dry density but on the wet side of the optimum, the surface

of the compacted soil mantle will roll under the dynamic compactive load. This is

unsuitable for road construction since each component of the pavement structure is to

be placed under dynamic conditions which will induce the rolling action of the

subgrade surface and cause structural failure of the new pavement. The foundations

or bedding of the sewer and slab-on-grade will be placed on a subgrade which will

not be subjected to impact loads. Therefore, the structurally compacted soil mantle

with the water content on the wet side or dry side of the optimum will provide an

adequate subgrade for the construction.

The presence of boulders will prevent transmission of the compactive energy into the

underlying material to be compacted. If an appreciable amount of boulders over

15 cm in size is mixed with the material, it must either be sorted or must not be used

for structural backfill and/or construction of engineered fill.


5.0 GROUNDWATER CONDITIONS

Groundwater seepage encountered in the boreholes during augering was recorded on

the borehole logs. The monitoring wells installed in the boreholes were also checked

for the presence of groundwater on August 5, 2016. The recorded levels are

summarized in Table 2.

Table 2 - Groundwater Levels

BH No. Borehole

Depth (m)

Soil Colour Changes Brown to

Grey

Groundwater Level Upon Completion of

Drilling Measured

Groundwater Level

Depth (m) Depth (m) El. (m) Depth (m) El. (m)

1 6.3 6.3+ 5.9 268.9 1.3 273.5

2 7.8 5.6± Dry Dry 3.1 267.5

3 6.3 4.3± 1.7 265.0 2.6 264.1

4 6.3 4.3± 2.0 260.7 2.3 260.4

As shown above, the stabilized groundwater levels in the monitoring wells were

recorded at depths ranging from 1.3 to 3.1 m below the ground surface, or at

El. 260.4 to 273.5 m. The groundwater level represents wet sand layers within the till

deposit and it will fluctuate with the seasons.

The soil colour changes from brown to grey at depths ranging from 4.3 to 5.6± m

below the prevailing ground surface in Boreholes 2, 3 and 4. The revealed soil in

Borehole 1 remains brown within the investigated depth. The brown colour indicates

that the soils have oxidized.

Reference No. 1606-S168 12 In excavation, the yield of groundwater seepage may be some to moderate and can be

removed by conventional pumping from sumps. Further assessment through

hydrogeological study can confirm the groundwater condition and the appropriate

dewatering method when the excavation depth is determined.


6.0 DISCUSSION AND RECOMMENDATIONS

The investigation has disclosed that beneath a veneer of topsoil, the site is underlain

by strata of very loose to very dense, generally compact silty sand till, and compact to

very dense, generally very dense sandy silt till, with embedded very loose sand layers

at various depths and locations.

Groundwater was recorded in three of the boreholes upon completion of drilling. On

August 5, 2016, the groundwater level in the monitoring wells was recorded at depths

ranging from 1.3 to 3.1 m below the ground surface, or at El. 260.4 to 273.5 m.

Percolated water from precipitation trapped in the sand and silt layers may also be

encountered at shallower depths during excavation. The yield of groundwater during

excavation may be some to moderate, which can be removed by conventional

pumping from sumps.

The geotechnical findings which warrant special consideration are presented below:

1. The topsoil, 20 to 25 cm in thickness, must be stripped and removed as it is

unsuitable for engineering applications. Due to its high humus content, it will

generate volatile gases under anaerobic conditions. For the environmental as

well as the geotechnical well-being of the future development, the topsoil

should not be buried under any structure, or deeper than 1.2 m below the

exterior finish grade.

2. The in situ native soils are weathered to depths ranging from 0.7± to 2.0± m

below the prevailing ground surface. The weathered soil is generally loose and

is not suitable for foundation support. The weathered soils can be

subexcavated, assessed and properly recompacted in layers to engineered fill

specifications for footing construction.

Reference No. 1606-S168 14 3. The sound natural soils below the weathered zone are suitable for normal

spread and strip footing for house construction. The footing subgrade must be

inspected by a geotechnical engineer, or a geotechnical technician under the

supervision of a geotechnical engineer, to ensure that its condition is

compatible with the design of the foundation.

4. Where cut and fill is required for site grading, it is generally more economical

to place an engineered fill for normal footing, sewer and road construction.

The placement of engineered fill will include the removal of the weathered

soils before compacting the fill in layers.

5. For slab-on-grade construction, any weathered or loose soils should be

subexcavated, aerated and properly compacted prior to the placement of the

slab. The slab should be constructed on a granular base, 20 cm thick,

consisting of 20-mm Crusher-Run Limestone, or equivalent, compacted to its

maximum Standard Proctor dry density.

6. Perimeter subdrains and dampproofing of the foundation walls will be required

for basement construction. The subdrains should be shielded by a fabric filter

to prevent blockage by silting. Depending on the design elevation of the

basement structure, underfloor subdrains may also be required below the

basement floor; this can be further assessed after the design is finalized or at

the time of basement excavation.

7. A Class ‘B’ bedding is recommended for the design of the underground

services. The bedding material should consist of compacted 20-mm Crusher-

Run Limestone, or equivalent. Where extensive dewatering is required in a

saturated soil subgrade a Class ‘A’ bedding should be considered.

8. Excavation into the tills containing cobbles and boulders may require extra

effort and the use of a heavy-duty backhoe equipped with a rock ripper.

Boulders larger than 15 cm in size are not suitable for structural backfill and/or

the construction of engineering fill.

Reference No. 1606-S168 15 The recommendations appropriate for the project described in Section 2.0 are

presented herein. One must be aware that the subsurface conditions may vary

between boreholes. Should this become apparent during construction, a geotechnical

engineer must be consulted to determine whether the following recommendations

require revision.

6.1 Foundations

Based on the borehole findings, the footings for the proposed structures should be

placed below the weathered soils and onto the sound natural soils. As a general guide

for the design of foundations, the recommended soil bearing pressures and

corresponding suitable founding levels are presented in Table 3.

Table 3 - Founding Levels

BH No.

Recommended Maximum Allowable Soil Pressure (SLS)/ Factored Ultimate Soil Bearing Pressure (ULS) and

Suitable Founding Level

100 kPa (SLS) 160 kPa (ULS)



Depth (m) El. (m) Depth (m) El. (m) Depth (m) El. (m)

1 1.0 or + 273.8 or - 2.4 or + 272.4 or - 4.6 or + 270.2

2 1.0 or + 269.6 or - 2.4 or + 268.2 or - 3.2 or + 267.4

3 1.0 or + 265.7 or - - - 2.4 or + 264.3

4 - - 2.0 or + 260.7 or - 2.4 or + 260.3

The recommended soil-bearing pressures incorporate a safety factor of three against

shear failure of the underlying soils. The total and differential settlements of the

footings founded on the sound natural soils are estimated to be 25 mm and 15 mm,

respectively.

Reference No. 1606-S168 16 The footing subgrade must be inspected by a geotechnical engineer, or a geotechnical

technician under the supervision of a geotechnical engineer, to ensure that its

condition is compatible with the design of the foundation.

If groundwater seepage is encountered in the footing excavation, or where the

subgrade of the normal foundations is found to be wet, the subgrade should be

protected by a concrete mud-slab immediately after exposure. This will prevent

construction disturbance and costly rectification.

The foundations exposed to weathering, or in unheated areas, should have at least

1.6 m of earth cover for protection against frost action, or must be properly insulated.

Where earth fill is required for site grading, it is generally more practical and

economical to place engineered fill suitable for a Maximum Soil Pressure of 100 kPa

for normal footing construction. The requirements and procedures for engineered fill

construction are discussed in Section 6.2.

The footings must meet the requirements specified in the latest Ontario Building

Code. As a guide, the structure should be designed to resist an earthquake force

using Site Classification ‘D’ (stiff soils).

6.2 Engineered Fill

Where earth fill is required for site grading, it is generally more economical to place

engineered fill for normal footing, underground services and pavement construction.

The engineering requirements for a certifiable fill for pavement construction,

municipal services, slab-on-grade, and footings designed with a Maximum Allowable

Soil Pressure (SLS) of 100 kPa and a Factored Ultimate Soil Bearing Pressure (ULS)

of 160 kPa are presented below:

Reference No. 1606-S168 17 1. All of the topsoil and organics must be removed, and the subgrade must be

inspected and proof-rolled prior to any fill placement. The weathered soil

must be subexcavated, sorted free of topsoil inclusions and deleterious

materials, if any, aerated and properly compacted in layers.

2. Inorganic soils must be used for backfilling, and they must be uniformly

compacted in lifts 20 cm thick to 98% or + of their maximum Standard Proctor

dry density up to the proposed finished grade and/or slab-on-grade subgrade.

The soil moisture must be properly controlled on the wet side of the optimum.

If the house foundations are to be built soon after the fill placement, the

densification process for the engineered fill must be increased to 100% of the

maximum Standard Proctor compaction.

3. If imported fill is to be used, the hauler is responsible for its environmental

quality and must provide a document to certify that the material is free of

hazardous contaminants.

4. If the engineered fill is to be left over the winter months, adequate earth cover,

or equivalent, must be provided for protection against frost action.

5. The engineered fill must extend over the entire graded area; the engineered fill

envelope and the finished elevations must be clearly and accurately defined in

the field, and they must be precisely documented by qualified surveyors.

Foundations partially on engineered fill must be reinforced by two

15-mm steel reinforcing bars in the footings and upper section of the

foundation walls, or be designed by a structural engineer, to properly distribute

the stress induced by the abrupt differential settlement (estimated to be

15± mm) between the natural soils and engineered fill.

6. The engineered fill must not be placed during the period from late November

to early April, when freezing ambient temperatures occur either persistently or

intermittently. This is to ensure that the fill is free of frozen soils, ice or snow.

Reference No. 1606-S168 18 7. Where the ground is wet due to subsurface water seepage, an appropriate

subdrain scheme must be implemented prior to the fill placement.

8. Where the fill is to be placed on sloping ground steeper than 1 vertical:

3 horizontal, the face of the sloping ground must be flattened to 3 + so that it is

suitable for safe operation of the compactor and the required compaction can

be obtained.

9. The fill operation must be inspected on a full-time basis by a technician under

the direction of a geotechnical engineer.

10. The footing and underground services subgrade must be inspected by the

geotechnical consulting firm that inspected the engineered fill placement. This

is to ensure that the foundations are placed within the engineered fill envelope,

and the integrity of the fill has not been compromised by interim construction,

environmental degradation and/or disturbance by the footing excavation.

11. Any excavation carried out in certified engineered fill must be reported to the

geotechnical consultant who supervised the fill placement in order to

document the locations of the excavation and/or to supervise reinstatement of

the excavated areas to engineered fill status. If construction on the engineered

fill does not commence within a period of 2 years from the date of

certification, the condition of the engineered fill must be assessed for

re-certification.

12. Despite stringent control in the placement of the engineered fill, variations in

soil type and density may occur in the engineered fill. Therefore, the strip

footings and the upper section of the foundation walls constructed on the

engineered fill will require continuous reinforcement with steel bars,

depending on the uniformity of the soils in the engineered fill and the

thickness of the engineered fill underlying the foundations. Should the

footings and/or walls require reinforcement, the required number and size of

reinforcing bars must be assessed by considering the uniformity as well as the


thickness of the engineered fill beneath the foundations. In sewer

construction, the engineered fill is considered to have the same structural

proficiency as a natural inorganic soil.

6.3 Basement and Slab-On-Grade

The basement structures should be designed to sustain the lateral earth pressure and

applicable surcharge loads which can be calculated using the soil parameters listed in

Section 6.9.

The subgrade for the slab-on-grade construction must consist of sound natural soils or

properly compacted inorganic earth fill. In preparation of the subgrade, the subgrade

must be inspected and assessed by proof-rolling. The badly weathered soils or any

soft or loose soils should be subexcavated, sorted free of any deleterious material,

aerated and uniformly compacted to 98% or + of its maximum Standard Proctor dry

density. If the deleterious materials cannot be sorted, the soils should be replaced by

properly compacted, organic-free earth fill.

Any new material for raising the grade should consist of organic-free soil compacted

to at least 98% of its maximum Standard Proctor dry density.

If the subgrade has been loosened due to construction traffic, it must be proof-rolled

before placement of the granular base.

The slab should be constructed on a granular base, 20 cm thick, consisting of

20-mm Crusher-Run Limestone, or equivalent, compacted to its maximum Standard

Proctor dry density.

Reference No. 1606-S168 20 A Modulus of Subgrade Reaction of 25 MPa/m can be used for the design of the floor

slab.

Where the subgrade is found to be wet, floor subdrains should be provided and

connected to a positive outlet. A vapour barrier should be placed at the crown level

of the floor subdrains to prevent upfiltration of moisture that may wet the floor. The

necessity to implement these measures can be assessed during construction.

The slab-on-grade in open areas should be designed to tolerate frost heave, and the

grading around the slab-on-grade and building structure must be such that it directs

runoff away from the structures.

6.4 Underground Services

The subgrade for the underground services should consist of sound natural soil or

properly compacted, organic-free earth fill. Where badly weathered or loose soil is

encountered, it should be subexcavated and replaced with bedding material

compacted to at least 95% or + of its Standard Proctor compaction.

A Class ‘B’ bedding is recommended for the underground services construction. The

bedding material should consist of compacted 20-mm Crusher-Run Limestone, or

equivalent, as approved by a geotechnical engineer. Where extensive dewatering is

required in saturated soil subgrade during sewer construction, a Class ‘A’ bedding

should be considered.

In order to prevent pipe floatation when the sewer trench is deluged with water, a soil

cover at least equal in thickness to the diameter of the pipe should be in place at all

times after completion of the pipe installation.

Reference No. 1606-S168 21 Where the sand and/or silt subgrade is encountered, the sewer joints should be leak-

proof, or wrapped with a waterproof membrane. This is to prevent the infiltration of

fines from the subgrade through inadvertent faulty joints. The necessity to implement

these measures can best be determined during sewer construction.

Openings to subdrains and catch basins should be shielded with a fabric filter to

prevent blockage by silting.

Sewer excavation must be sloped at 1 vertical:1 or + horizontal for stability.

Alternatively, a trench box can be used for the construction of the sewer.

For estimation purposes for the anode weight requirements, the electrical resistivity

which has been determined for the disclosed soils can be used. This, however, can be

confirmed by testing the soil along the water main alignment at the time of sewer

construction. Moreover, the anode weight must meet the minimum requirements

specified by York Region and City of Orillia.

6.5 Backfilling in Trenches and Excavated Areas

The on-site inorganic soils are generally suitable to use for trench backfill. The

backfill in the trenches should be compacted to at least 95% of its maximum Standard

Proctor dry density. Aeration of the wet in situ soils may be required for proper

compaction.

The backfill in service trenches should be compacted to at least 95% of its maximum

Standard Proctor dry density. In the zone within 1.0 m below the road subgrade, the

materials should be compacted with the water content 2% to 3% drier than the

optimum, and the compaction should be increased to at least 98% of the respective

maximum Standard Proctor dry density. This is to provide the required stiffness for

Reference No. 1606-S168 22 pavement construction. In the lower zone, the compaction should be carried out on

the wet side of the optimum; this allows a wider latitude of lift thickness. Backfill

below any slab-on-grade that is sensitive to settlement must be compacted to at least

98% of its maximum Standard Proctor dry density.

In normal construction practice, the problem areas of settlement largely occur

adjacent to manholes, catch basins, services crossings, foundation walls and columns.

In areas which are inaccessible to a heavy compactor, imported sand backfill should

be used. Unless compaction of the backfill is carefully performed, the interface of

the native soils and the sand backfill will have to be flooded for a period of several

days.

The narrow trenches for services crossings should be cut at 1 vertical:

2 or + horizontal so that the backfill can be effectively compacted. Otherwise, soil

arching will prevent the achievement of proper compaction. The lift of each backfill

layer should either be limited to a thickness of 20 cm, or the thickness should be

determined by test strips.

One must be aware of the possible consequences during trench backfilling and

exercise caution as described below:

• When construction is carried out in freezing winter weather, allowance should

be made for these following conditions. Despite stringent backfill monitoring,

frozen soil layers may inadvertently be mixed with the structural trench

backfill. Should the in situ soil have a water content on the dry side of the

optimum, it would be impossible to wet the soil due to the freezing condition,

rendering difficulties in obtaining uniform and proper compaction.

Furthermore, the freezing condition will prevent flooding of the backfill when

it is required, such as in a narrow vertical trench section, or when the trench


box is removed. The above will invariably cause backfill settlement that may

become evident within 1 to several years, depending on the depth of the trench

which has been backfilled.

• In areas where the underground services construction is carried out during the

winter months, prolonged exposure of the trench walls will result in frost

heave within the soil mantle of the walls. This may result in some settlement

as the frost recedes, and repair costs will be incurred prior to final surfacing of

the new pavement and the slab-on-grade.

• To backfill a deep trench, one must be aware that future settlement is to be

expected, unless the side of the cut is flattened to at least 1 vertical:

1.5+ horizontal, and the lifts of the fill and its moisture content are stringently

controlled; i.e., lifts should be no more than 20 cm (or less if the backfilling

conditions dictate) and uniformly compacted to achieve at least 95% of the

maximum Standard Proctor dry density, with the moisture content on the wet

side of the optimum.

• It is often difficult to achieve uniform compaction of the backfill in the lower

vertical section of a trench which is an open cut or is stabilized by a trench

box, particularly in the sector close to the trench walls or the sides of the box.

These sectors must be backfilled with sand. In a trench stabilized by a trench

box, the void left after the removal of the box will be filled by the backfill. It

is necessary to backfill this sector with sand, and the compacted backfill must

be flooded for 1 day, prior to the placement of the backfill above this sector,

i.e., in the upper sloped trench section. This measure is necessary in order to

prevent consolidation of inadvertent voids and loose backfill which will

compromise the compaction of the backfill in the upper section. In areas

where groundwater movement is expected in the sand fill mantle, anti-seepage

collars should be provided.


6.6 Garages, Driveways, Interlocking Stone Pavement and Landscaping

The driveways at the entrances to the garages can be backfilled with non-frost-

susceptible granular material, with a frost taper at a slope of 1 vertical:1 horizontal.

The recommended scheme is illustrated in Diagram 1.

Diagram 1 - Frost Protection Measures (Garage)

Interlocking stone pavement, slab-on-grade and landscaping structures in areas which

are sensitive to frost-induced ground movement, such as in front of building

entrances, must be constructed on a free-draining, non-frost-susceptible granular

material such as Granular ‘B’. This material must extend to at least 0.3 to 1.2 m

below the slab or pavement surface, depending on the degree of tolerance of ground

movement, and be provided with positive drainage, such as weeper subdrains

connected to manholes or catch basins. Alternatively, the landscaping structures,

slab-on-grade and interlocking stone pavement should be properly insulated with

50-mm Styrofoam, or equivalent.

The grading around structures must be such that it directs runoff away from the

structures.


6.7 Pavement Design

The recommended pavement design for the access roads and driveways is presented

in Table 4.

Table 4 - Pavement Design

Course Thickness (mm) OPS Specifications

Asphalt Surface 40 HL-3

Asphalt Binder 60 HL-8

Granular Base 150 OPSS Granular ‘A’ or equivalent

Granular Sub-base Local Collector

350 450

OPSS Granular ‘B’ or equivalent

In preparation of the pavement subgrade, topsoil must be removed and final subgrade

must be proof-rolled. Any soft spots, as identified, should be subexcavated, sorted

free of any concentrated topsoil, if encountered, aerated and properly compacted or

replaced with uniformly compacted inorganic earth fill.

The granular bases should be compacted to their maximum Standard Proctor dry

density.

In the zone within 1.0 m below the pavement subgrade, the backfill should be

compacted to at least 98% of its maximum Standard Proctor dry density, with the

water content at 2% to 3% drier than the optimum. In the lower zone, a 95% or +

Standard Proctor compaction is considered adequate.

Reference No. 1606-S168 26 The subgrade will suffer a strength regression if water is allowed to saturate the

mantle. The following measures should, therefore, be incorporated in the

construction procedures and road design:

• If the road construction does not immediately follow the trench backfilling, the

subgrade should be properly crowned and smooth-rolled to allow interim

precipitation to be properly drained.

• Lot areas adjacent to the roads should be properly graded to prevent ponding of

large amounts of water. Otherwise, the water will seep into the subgrade mantle

and induce a regression of the subgrade strength with costly consequences for

the pavement construction.

• Curb subdrains will be required on both sides of the roadway. The subdrains

should consist of filter-sleeved weepers to prevent blockage by silting.

• If the pavement is to be constructed during wet seasons and extensively soft

subgrade occurs, the granular sub-base should be thickened in order to

compensate for the inadequate strength of the subgrade. This can be assessed

during construction.

6.8 Stormwater Management Pond

A detailed design of the Stormwater Management Pond (SWM) pond, was not

available at the time of report preparation. Based on the Conceptual Development

Plan prepared by MHBC Planning Urban Design & Landscape Architecture, it is

understood that a SWM pond is proposed at the northeast corner of the property at the

vicinity of Borehole 4, where the soil stratigraphy consists of silty sand till and sandy

silt till material with a trace to some clay and a trace of gravel. Groundwater was

recorded at a depth of 2.3 m below the prevailing ground surface in this borehole, on

August 5, 2016.

Reference No. 1606-S168 27 Depending on the design grades, the pond will likely be constructed by excavating

into the till strata. Where the sides or bottom of the pond consist of significant strata

of sand and silt, an impermeable geosynthetic membrane or a clay liner should be

provided as a water barrier. The thickness of the clay liner or surchange above the

geosysthetic membrane should also be capable to overcome the hydrostatic pressure

at the bottom of the liner as recorded in the monitoring wells. The clay liner should

be compacted to 98% of its maximum Standard Proctor dry density.

The coefficients of permeability and the recommended infiltration rates for the design

of the pond are presented in Table 5.

Table 5 - Coefficients of Permeability and Infiltration Rates

Soil Coefficient of Permeability (cm/sec) Percolation Time (min/cm)

Silty Sand Till 10-5 15±

Sandy Silt Till 10-6 10±

The estimated infiltration rates are based on the grain size distribution of soil samples

and are provided for reference only. In situ infiltration tests can be carried out to

verify the above estimation.

The sides of the pond should be sloped at 1 vertical:4 or + horizontal below the wet

perimeter and should be 1 vertical:3 or + horizontal in dry areas. All slopes must be

vegetated and/or sodded to prevent runoff erosion.

For berm construction, the topsoil must be removed and the subgrade must be proof-

rolled. Inorganic soil material consisting of silty clay must be used and compacted to

at least 95% of its maximum Standard Proctor dry density. Berm shall be designed

with a minimum top width of 2.0 m with a 3:1 maximum side slope on the outside.

Reference No. 1606-S168 28 The core of the berm shall be constructed with engineered fill on the basis of the

recommendation in Section of 6.2 of this report.

The soil bearing capacity given in Section 6.1 can be used for the design of

foundations for the control structures. The footings must be placed below the

scouring depths and be provided with a minimum earth cover of 1.6 m for protection

against frost damage. The inlet and outlet of the pond must be lined with gabion

mats for protection against scouring.

6.9 Soil Parameters

The recommended soil parameters for the project design are given in Table 6.

Table 6 - Soil Parameters

Unit Weight and Bulk Factor Unit Weight

(kN/m3)

Estimated

Bulk Factor

Bulk Submerged Loose Compacted

Sand 20.5 10.5 1.20 1.00

Silty Sand Till/ Sandy Silt Till 22.5 12.5 1.33 1.05

Lateral Earth Pressure Coefficients

Active Ka

At Rest K0

Passive Kp

Compacted Earth Fill/Sand 0.40 0.52 2.00

Silty Sand Till/Sandy Silt Till 0.33 0.48 3.00

6.10 Excavation

Excavation should be carried out in accordance with Ontario Regulation 213/91.

Reference No. 1606-S168 29 Excavations in excess of 1.2 m should be sloped at 1 vertical:1 or + horizontal for

stability. For excavation purposes, the types of soils are classified in Table 7.

Table 7 - Classification of Soils for Excavation

Material Type

Sound natural Tills 2

Weathered Soils, Earth Fill and drained Sand 3

In excavations, the groundwater yield from the native till deposits will be some to

moderate, which can be collected to a sump pump and removed by conventional

pumping.

The appropriate method of dewatering should be determined by further assessment of

hydrogeological study.

The tills contain occasional cobbles and boulders. Extra effort and a properly

equipped backhoe will be required for excavation. Boulders larger than 15 cm in size

are not suitable for structural backfill and/or construction of engineered fill.

Prospective contractors must assess the in situ subsurface conditions prior to

excavation by digging test pits to at least 0.5 m below the invert elevation. These test

pits should be allowed to remain open for a period of at least 4 hours to assess the

trenching conditions.

LIST OF ABBREVIATIONS AND DESCRIPTION OF TERMS The abbreviations and terms commonly employed on the borehole logs and figures, and in the text of the report, are as follows: SAMPLE TYPES

AS Auger sample CS Chunk sample DO Drive open (split spoon) DS Denison type sample FS Foil sample RC Rock core (with size and percentage

recovery) ST Slotted tube TO Thin-walled, open TP Thin-walled, piston WS Wash sample PENETRATION RESISTANCE

Dynamic Cone Penetration Resistance:

A continuous profile showing the number of blows for each foot of penetration of a 2-inch diameter, 90° point cone driven by a 140-pound hammer falling 30 inches. Plotted as ‘ • ’

Standard Penetration Resistance or ‘N’ Value:

The number of blows of a 140-pound hammer falling 30 inches required to advance a 2-inch O.D. drive open sampler one foot into undisturbed soil. Plotted as ‘’

WH Sampler advanced by static weight PH Sampler advanced by hydraulic pressure PM Sampler advanced by manual pressure NP No penetration

SOIL DESCRIPTION

Cohesionless Soils:

‘N’ (blows/ft) Relative Density

0 to 4 very loose 4 to 10 loose

10 to 30 compact 30 to 50 dense

over 50 very dense

Cohesive Soils:

Undrained Shear Strength (ksf) ‘N’ (blows/ft) Consistency

less than 0.25 0 to 2 very soft 0.25 to 0.50 2 to 4 soft 0.50 to 1.0 4 to 8 firm 1.0 to 2.0 8 to 16 stiff 2.0 to 4.0 16 to 32 very stiff

over 4.0 over 32 hard

Method of Determination of Undrained Shear Strength of Cohesive Soils:

x 0.0 Field vane test in borehole; the number denotes the sensitivity to remoulding

Laboratory vane test

Compression test in laboratory

For a saturated cohesive soil, the undrained shear strength is taken as one half of the undrained compressive strength

METRIC CONVERSION FACTORS 1 ft = 0.3048 metres 1 inch = 25.4 mm 1lb = 0.454 kg 1ksf = 47.88 kPa

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Job Number: 1606-S168

Ground Surface

SAMPLES Atterberg Limits

PL LL

Figure No.:

Method of Boring: Flight-Auger

Drilling Date: July 19, 2016

LOG OF BOREHOLE NO.: 1

Job Location: 3879 Town Line, City of Orillia

Project Description: Proposed Residential Development

SOIL ENGINEERS LTD.1 of 1Page:

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Reference No: 1606-S168

U.S. BUREAU OF SOILS CLASSIFICATION

COARSE

UNIFIED SOIL CLASSIFICATION

COARSE

Project: Residential Development BH./Sa. 2/4 4/5Location: 38796 Town Line, City of Orillia Liquid Limit (%) = - -

Plastic Limit (%) = - -Borehole No: 2 4 Plasticity Index (%) = - -Sample No: 4 5 Moisture Content (%) = 10 8Depth (m): 2.5 3.2 Estimated Permeability Elevation (m): 268.1 259.5 (cm./sec.) = 10-5 10-5

Classification of Sample [& Group Symbol]: SAND, Tilltrs. of clay and gravel

SILT & CLAY

Figure: 5

COARSE

MEDIUM

FINE

CLAY

SAND

MEDIUMFINE

GRAVEL

GRAIN SIZE DISTRIBUTION

SAND

V. FINE

GRAVELSILT

COARSE FINEFINE

3" 2-1/2" 2" 1-1/2" 1" 3/4" 1/2" 3/8" 4 8 10 16 20 30 40 50 60 100 140 200 270 325

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

Perc

ent P

assi

ng

Grain Size in millimeters

BH.4/Sa.5

BH.2/Sa.4

255

273

271

269

267

265

263

261

259

257

255

4

13

14

24

27

100

100

3

14

14

32

100

100

100

100

3

11

14

100

100

100

100

3

6

5

54

100

100

100

1274.8

2270.6

3266.7

4262.7

Soil Engineers Ltd.CONSULTING ENGINEERSGEOTECHNICAL | ENVIRONMENTAL | HYDROGEOLOGICAL | BUILDING SCIENCE

BH No.El.

WL (STABILIZED)

Legend

TOPSOIL SAND SILTY SAND TILL SANDY SILT TILL

Job Number:

Job Location:

Project Description:

1606-S168

3879 Town Line, City of Orillia

Proposed Residential Development

Report Date: August 2016

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